[llvm] [PHIElimination] Reuse existing COPY in predecessor basic block (PR #131837)

[via llvm-commits]

macurtis-amd wrote:

> Check this PR: https://github.com/llvm/llvm-project/pull/146806
@macurtis-amd Can you try it out too please?

@guy-david I'm still seeing the hang with [0629fffe95](https://github.com/llvm/llvm-project/pull/146806/commits/0629fffe954d6279a476d8d099565caff6135420).

https://github.com/llvm/llvm-project/pull/131837